Droplet forming methods making use of electrostatic force are known as arts for dispensing minute amounts of liquid and forming droplets. For example, Patent Documents 1 and 2 disclose arts for forming droplets by applying a pulse voltage between a substrate disposed across a predetermined distance from a nozzle tip, and a liquid, inside the nozzle, to draw out the liquid from the nozzle tip. Of these, in the Patent Document 1, it is described that the volume of the droplet can be controlled by controlling the pulse height of the pulse voltage applied between the liquid inside the nozzle and the substrate. In the Patent Document 2, it is described that the volume of the droplet can be controlled by controlling the pulse height of the pulse voltage, a pulse width of the pulse voltage, or the distance between the nozzle tip and the substrate.
Also, Patent Document 3 discloses an inkjet recording device that uses electrostatic force. In this Patent Document 3 is disclosed an art for controlling a pulse height, pulse width, pulse frequency, etc. of a pulse voltage, applied to a discharge electrode inside a nozzle, on the basis of ink characteristics (toner concentration).
Patent Document 1: Japanese Published Unexamined Patent Application No. 2001-038911
Patent Document 2: International Patent Publication Pamphlet No. 03/020418
Patent Document 3: Patent Publication No. 2885716